"It's a tossup on who is a tougher leader, President Barack Obama or President Vladimir Putin, as Americans weigh the heavyweight standoff over Ukraine," said Tim Malloy, assistant director of the Quinnipiac University Poll.

Respondents gave "mixed signals" on Obama's handling of the issue as Russia annexed the Crimea region of Ukraine, and made threats regarding the rest of the country, the poll said.

"A total of 80% of American voters are 'very concerned' or 'somewhat concerned' that the Ukraine situation could lead to a larger regional conflict with U.S. military involvement. ...

"Only 24% of American voters compare Russian President Vladimir Putin's actions in Ukraine to Adolf Hitler's actions prior to the outbreak of World War II, while 51% say that is too strong a comparison and 21% don't know enough about that pre-war history."